BRASILIA, BRAZIL — For generations, the Awa lived far from the rest of humanity, picking fruit, hunting pigs and monkeys, and following the seasons’ rhythms in their patch of the lush Brazilian Amazon rainforest.

Then the rest of the world found the Awa.

Loggers and ranchers came, cutting into the tribe’s ancestral lands in search of profits. So did a rail line on which trains shuttle tons of iron ore through the forest, from mines in the heart of the Amazon to Atlantic Ocean ports, with much of it headed for Chinese steel mills.

The threat to the Awa grew so grave that it caught the attention of the British-based indigenous rights group Survival International, which designated them “the world’s most endangered tribe” and made their preservation its top campaign priority this year.

While the Awa may face the most immediate threat, tribes across Brazil are locked in the same struggle as they battle loggers, ranchers, miners and farmers who often invade government-demarcated reserves.

Brazil’s maturing economy is driving much of the development, as is renewed strength of the country’s farm sector, which recently pushed through reforms loosening Brazil’s forest protection law.

Watchdog groups say more conflict is inevitable as government-backed projects such as hydroelectric dams and roads bring thousands of settlers to remote areas. Two bills now working their way through Brazil’s National Congress would further open indigenous territory to development and potentially weaken tribes’ hold on their land.

“We’re seeing that the conflicts Indians are having are becoming more potent in recent years, with a series of violent clashes stoked by the agenda of the federal government to develop remote areas,” said Cleber Buzatto, executive director of the Brazil-based indigenous-rights group CIMI.

For the Awa and other tribes, however, contact with the outside world hasn’t just brought threats: Help is also on the way.

Farming concerns

The issue will take center stage during this month’s “People’s Summit” in Rio de Janeiro, a gathering linked to the annual World Social Forum, also in Brazil.

The summit is expected to draw thousands of activists to an alternative to the United Nations’ Rio+20 conference on sustainable development happening in Rio at the same time.

The plight of the formerly isolated Awa even drew the attention of Academy Award-winning actor Colin Firth, who appeared in a Survival International video urging people to contact Brazilian Justice Minister Jose Eduardo Cardozo and tell him to send police to protect indigenous reserves.

“This is our chance right now to actually do something,” Mr. Firth says in the clip.

Last Tuesday, Brazilian President Dilma Rousseff created two new nature reserves, as well as seven indigenous territories in the Amazon, covering thousands of square miles.

For Brazilian farm groups, protecting tens of thousands of indigenous people is too high a price to pay for blocking production of soy, beef and other agricultural goods, exports of which have helped fuel rising fortunes in Brazil and a growing middle class.

In total, 22 percent of the Amazon has been turned over to indigenous groups in addition to 11 percent elsewhere in Brazil.

“Who benefits from this? Not our country, which today enjoys the best and cheapest food in the world and boasts of being the globe’s second-largest food exporter,” Sen. Katia Abreu, president of Brazil’s National Agriculture and Livestock Federation, wrote in a recent opinion piece for the newspaper Folha de S. Paulo.

“Neither do the Indians, who as their numbers show don’t need more physical space, but sanitation, education and an efficient health system. They need, in short, a better life, like all of us.”

At a news conference last week, Ms. Abreu added that any expansion of indigenous reserves beyond those originally established before 1993 is “not in accordance with the constitution.”

Federal agencies responsible for protecting the indigenous say they are doing virtually everything in their power to stop the encroachment, but they acknowledge their powers are limited while policing with limited means roughly 480,000 square miles of Indian reserves, an area larger than Sweden.

As a sign of the government’s limited reach in the Amazon, about 180 illegal sawmills have sprung up around the Awa’s land, often in plain sight, with giant trucks roaring through forest roads day and night bringing fresh lumber.

In Mato Grosso do Sul state, the 40,000-strong Guarani-Kaiowa tribe has seen many members pushed into makeshift camps along highways and tent villages along rivers, as they lobby to have their lands recognized legally.

Economic hardship has sparked a rash of suicides. More than 550 tribe members killed themselves from 2000 to 2011, according to statistics from Brazil’s secretariat on indigenous health.

An additional 282 were murdered, mostly in fights over land, from 2003 to 2011, according to CIMI, making up half of all native people killed in Brazil during the period.

Guarani-Kaiowa elder Nisio Gomes was gunned down in November by masked men, his body dragged into a waiting pickup truck and spirited away. His remains have yet to be found.

“We’ve gone through many difficulties, and I can’t even walk in the cities because of the risks,” said Valmir Gomes, Nisio’s son, while lobbying in Brasilia for the tribe’s own reserve. “We need the demarcation so that we can freely walk on our own lands.”

‘Stay in the forest’

Indigenous activists, however, say experience has shown demarcating land is clearly not enough.

CIMI registered 33 invasions of reserves in 2010, the most recent year for which statistics are available.

At least 10 of those conflicts turned deadly, with violent fights breaking out between the indigenous and those entering the land. That’s about the same number of invasions and conflicts CIMI has reported annually over the past five years.

The Brazilian government officially recognized the Awa reserve - some 455 square miles in Maranhao, Brazil’s poorest state - in 2005, but the incursions continued. That’s included people entering with guns and threatening federal agents charged with patrolling the area.

Satellite images show that nearly a third of the Awa’s forest has been logged and much of the area taken over by cattle ranchers and farmers.

Of the tribe’s few hundred members, an estimated 60 to 100 of them have never had any contact with the outside world.

In a Survival International video, Wamaxua Awa, a young Awa, says he spent years running away from outsiders encroaching on tribal land before recently leaving the forest and living in a village with other Awa.

His three brothers still live deep inside the forest.

“When I lived in the forest I had a good life,” he says in a soft, timid voice while wearing a modern, V-neck shirt. “Now if I meet one of the uncontacted Awa in the forest, I’ll say, ‘Don’t leave! Stay in the forest.’ I’d tell them to stay, that it’s better in the forest. ‘There’s nothing in the outside for you,’ I’d say.”